"The impacts of climate change on agriculture and the food system will profoundly alter the way we grow and produce food. This will affect different parts of the world in radically different ways, but all regions will have to change their current approach to what they grow and eat," said Sonja Vermeulen, the head of research at CCAFS and the lead author of the Climate Change and Food Security report.

The report warns that yields of the three biggest crops in terms of calories provided - maize, rice and wheat - will decrease in many developing countries as temperatures rise and rainfall becomes more unpredictable.

Looking ahead to 2050, the report estimates that irrigated wheat yields in developing countries will fall by 13 percent and irrigated rice in these same countries will drop by 15 percent. In Africa, farmers of maize could lose up to 20 percent of their yields.

Vegetable sources of protein will not fare much better, the report notes, with soybeans, millet, lentils and cowpea particularly vulnerable to heat stress.

Higher temperatures and unpredictable rainfall impact more than just crop yields, according to CCAFS' Philip Thornton. "Ecosystem changes due to climate change may spawn shifts in the intensity of pests and diseases - including potato blight and beetles - that will further limit food production. Indeed, even if crops could withstand increased temperatures and decreased rainfall, their yields could drop because of these scourges," he explained.

Robert Zougmoré, CCAFS' regional program leader for West Africa, says that farmers and consumers in developing nations will be the hardest hit. "The problems that climate change produces in the fields will be tackled in industrialized countries. It is the smallholder farmers in Africa and South Asia and the urban poor who spend too much of their wages on food; these are the people who will have less to eat in the near future unless we adapt at a much faster pace."

The report lays out the challenges - lowering the emissions footprint of food production (currently accounting for one-third of all emissions) and adapting food systems to changing climates - that must be confronted as the world population grows to an estimated 9 to 10 billion people by 2050.

Feeding this many new people means that farmers and food producers must adapt, warns Thornton, who adds that farmers need help now. "They can't face these complex, interrelated problems, which vary from crop to crop and region to region, alone. They need support from the highest levels," he concluded.